Gas-blast circuit breaker



Dec. 24, 196.8 J, w. BEATTY ET AL GAS-BLAST CIRCUIT BREAKER 3 Sheets-Sheet l Filed Sept.. 14, 1965 I ATTORN-)h y J.w.BEAr1-Y ETAL' GAS-BLAST CIRCUIT BREAKER 3 Sheets-Sheet 2 Filed Sept. 14, 1965 /N VENTO/Qs: JOHN VV. BEATTY, GEORGE /V/cNE/R, um@

ATTORNEY Dec. 24, 1968 J. w. BEATTY l-:TAL 3,418,440

\ GAS-BLAST CIRCUIT BREAKER Filed Sept. 14, 1965 3 Sheets-Sheet 3 /NvE/vrons: JOHN VV. BEATTY, GEORGE Mc/VE/R,

BY im ATTORNEY nited States Patent O 3,418,440 GAS-BLAST CIRCUIT BREAKER .lohn W. Beatty, Newtown Square, and George McNeir,

Lansdowne, Pa., assignors to General Electric Company, a corporation of New York Filed Sept. 14, 1965, Ser. No. 487,206 10 Claims. (Cl. 200-148) ABSTRACT OF THE DISCLGSURE Gas-blast circuit breaker in which the electrodes of the breaker are normally spaced-apart by a relatively large amount to provide a high dielectric strength, but during high current interruptions the electrode spacing is reduced to provide for higher interrupting capacity than is available with the normal large electrode-spacing. Immediately after interruption, the normal large electrode-spacing is restored. The above reduction in electrode-spacing is produced by an electromagnet in series with the electrodes, which also produces a radial field for arc rotation and force for opening an auxiliary blast valve.

This invention relates to a gas-blast circuit breaker and, more particularly, relates to means for improving the interrupting ability of such a circuit breaker.

The usual gas-blast circuit breaker comprises means for establishing an electric arc across a gap between two electrodes and means for directing a high velocity blast of gas into the arcing region. The purpose of the gas blast is to cool the arc and to scavenge the arcing region of arcing products so as to increase the rate at which dielectric strength is built up across the gap when the current Zero point is reached. By increasing this rate of dielectric recovery, it is possible to improve the ability of the gap to withstand the usual recovery voltage transient that builds up as soon as a current zero is reached, thus improving the interrupting ability of the circuit breaker.

For extra high voltage applications, the spacing between the electrodes of an open circuit breaker must be relatively great in order to meet the severe insulation requirements these high voltages impose. It may seem that it should not be a diflicult matter to provide the relatively great inter-electrode spacing required; but when the required spacing has `been provided, an impairment in current-interrupting ability has been noted. In other words, the inter-electrode spacing most favorable for interruption has been found to be substantially shorter than that required to withstand the extra high voltages.

An object of the present invention is to provide a new and improved gas-blast circuit breaker in which the relatively great inter-electrode spacing required for extra high voltage applications is provided without detracting from the ability that the breaker has to interrupt currents at shorter inter-electrode spacings.

In carrying out our invention in one form, we provide a pair of electrodes that are normally spaced-apart by the relatively large amount needed to meet extra high voltage insulating requirements. One of these electrodes is mounted for movement to and from the other electrode. Actuating means responsive to current through the movable electrode is provided for moving the movable electrode toward the other electrode when the current is relatively high. When the current falls below a predetermined level, the movable electrode is quickly returned to its normal position to reestablish the relatively large inter-electrode spacing originally present.

It has been found that the interrupting ability of a gas blast circuit breaker can be improved by rotating one of the terminals of the arc during the interrupting period. This can be done by providing a radial magnetic field that extends transversely of the arc.

Another object of our invention is to provide means capable of performing the dual function of (l) producing the desired magnetic field for arc rotation and (2) producing the force required for shortening the inter-electrode gap during high current interruptions.

A common type of gas-blast circuit breaker is the axialblast type breaker. In such a breaker the blast of gas flows axially of the arc, first passing the one electrode which is normally referred to as the upstream electrode and then passing the other electrode, which is referred to as the downstream electrode. It has been found that the interrupting capacity of the axial-blast type breaker can be improved by providing an auxiliary blast passage in the upstream electrode, through which an auxiliary blast is directed during interruption.

Another object of our invention is to provide new and improved means for controlling the ow of gas through this auxiliary blast passage.

Still another object is to control this auxiliary blast with a valve actuated by force derived from the same means that is used for effecting the above-described control of the position of the movable electrode.

In carrying out these additional objects in accordance with one form of our invention, we provide an auxiliary blast passage leading through the upstream electrode. Flow through this passage is controlled by a normally-closed auxiliary blast valve. The normally-closed auxiliary blast valve is controlled by current responsive means which opens the auxiliary blast valve in response to current through the upstream electrode exceeding a predetermined Value. In a preferred form lof the invention, the movable valve element of the auxiliary blast valve is coupled to the previously-described movable electrode, and both the movable electrode and the auxiliary blast valve are operated by the current responsive valve-control means. When the current through the electrode exceeds a predetermined value, the current responsive valve-control means drives the movable electrode into its shorter-gap, preferred interrupting, position and also drives the movable valve element into a position that opens the auxiliary blast valve.

For a better understanding of our invention, reference maybe had to the following description taken in conjunction with the accompanying drawings, wherein:

FIG. l is a view, partly in section, of a gas-blast circuit breaker embodying one form of our invention.

FIG. 2 is -an enlarged sectional view of a portion of a circuit breaker of FIG. 1. The parts are shown in the positions they occupy when the circuit breaker is closed.

FIG. 3 illustrates the parts of FIG. 2 during a high current interruption.

FIG. 4 is a sectional view taken along the line 4-4 of FIG. 3.

FIG. 5 is a sectional view taken along the line 5-5 of FIG. 3.

FIG. 6 is an enlarged exploded view of a portion of FIG. 2.

FIG. 7 is a sectional view similar to that of FIG. 2 but showing a modified form of the invention.

Referring now to FIG. 1, the circuit interrupter shown therein is of the sustained-pressure, gas-blast type described and claimed in U.S. Patent 2,783,338 to Beatty assigned to the assignee of the present invention. Only those parts of the interrupter that are considered necessary to provide an understanding of the present invention have been shown in FIG. l. In this respect, only the right hand portion of the interrupter has been shown in section inasmuch as the interrupter is generally symmetrical with respect to a vertical plane and the left hand portion is substantially identical to the right hand portion. As described in detail in my above-mentioned patent, the interrupter comprises a casing 12 which is normally filled with pressurized gas to define an interrupting chamber 11. Located within the interrupting chamber 11 are a pair of relatively movable contacts 14 and 16 which can be separated to draw an arc within the pressurized gas within the chamber 11. The contact 14 is relatively stationary, whereas the other contact 16 is mounted for pivotal motion about a fixed, current-carrying pivot 18. When the movable contact 16 is driven clockwise about the pivot 18 from its solid-line closed position of FIG. l, an arc is established in the region where the contacts part. The movable contact 16 is shown by dotted lines in FIG. 1 in a partially-open position through which it passes during a circuit-interrupting operation after having established an arc.

The movable Contact 16 is supported by means of its current-carrying pivot 18 on a conductive bracket 19 that is preferably formed integral with a stationary cylinder 32. The cylinder 32 .at its lower end is suitably supported from a generally cylindrical casting 33. The

casting 33 at its lower end is suitably secured to a flange 35 rigidly carried by the stationary metallic casing 12.

For producing a gas blast to aid in extinguishing the a-rc, the cylindrical casting 33 contains a normally-closed exhaust passage 36 leading from the interrupting chamber 11 to the surrounding atmosphere. The casting 33 at its upper end is provided with a tubular nozzle-type electrode 38 having an orifice portion 39 at its outer end defining an inlet 37 to the exhaust passage 36. This inlet 37 is referred to hereinafter as the orice opening. The flow of arc-extinguishing gas through the tubular nozzle 38 and the exhaust passage 36 is controlled by means of a cy,

lindrically-shaped reciprocable blast valve member 40 located at the outer, or lower, end of the exhaust passage 36. This blast valve member 40 normally occupies a solid-line, closed position wherein its lower end face sealingly abuts against a stationary valve seat 34 carried by the exhaust casting 33.

During a circuit-interrupting operation, the movable blast valve member 40 is driven upwardly from its solid line, closed position of FIG. l through a partially open intermediate position shown in dotted lines in FIG. l. Opening of the valve member 40 allows pressurized gas in the chamber 11 to ow at high speed through the orifice opening 37 and nozzle 38 and out the exhaust passageway 36 past the valve member 40 to atmosphere, as indicated by `the arrows B of FIG. l. The manner in which the gas blast acts to extinguish the arc will soon be described in greater detail.

At its upper end, the cylindrical valve member 40 surrounds a projecting tubular support 41 upon which the valve member 40 is smoothly slidable. The tubular support 41 is fixed to the casting 33, preferably, by means of bolts (not shown) clamping the flange 41a to the top of casting 33. A compression spring 44 positioned between the movable valve member 40 and the lower end of support 41 tends to hold the valve member 40 in its closed position against the valve seat 34.

To protect the support 41 and the upper end of the valve member 40v from the harmful effects of arcing, a protective metallic tube `43 is positioned about these parts and is suitably secured to the support 41. Secured to the outer surface of this tube is a downstream probe or electrode 45, preferably of a refractory metal, which projects radially from the tube 43 and transversely into the path of the gas blast flowing through the passageway 36. As will soon appear more clearly, the downstream terminal of the arc is transferred to this electrode 45 during an interrupting operation and, after such transfer, occupies a position generally corresponding to that shown at 46. The downstream electrode is preferably constructed as shown and claimed in Patent No. 2,897,324 to Schneider, assigned to the assignee of the present invention, so that it has a non-streamlined upstream surface 48 that coacts with the gas blast to form a stagnation region upstream from the surface 48. The terminal of an arc such as 46 reaching the electrode 45 is captured within the stagnation region and thus prevented from being driven further downstream by the gas blast.

For controlling the operation of the movable blast valve 48 and movable contact 16, a combined operating mechanism QQ is provided. This mechanism 5 0 is preferably constructed in the manner disclosed and claimed in the aforementioned Beatty Patent 2,783,338, and its de- :tails form no part of the present invention. Generally speaking, this mechanism i() comprises a valve-controlling piston 51 and a contact-controlling piston 52 mounted within the cylinder 32. The valve-controlling piston 51 is coupled to the movable valve member 40 through a piston rod 54 suitably clamped to the valve member 40. The contactcontrolling piston 52, on the other hand, is connected to the movable contact 16 through a piston rod 58 and a cross head 59 secured to the piston rod. A link 60 pivotally joined to the cross head 59 at 61 and to the movable contact 16 at 62 interconnects the cross head 59 and the movable contact 16. When the valvecontrolling piston 51 is driven upwardly, it acts to open the valve member 40, and, simultaneously, to drive the contact-controlling piston 52 upwardly to produce opening movement of the movable contact member 16.

Opening movement of the contact member 16 first establishes an arc between the ends of the contacts 14 and 16. Shortly thereafter, however, the blast of gas which has been flowing through the orice opening 37, as indicated by the arrows B, forces the upstream terminal of the are on to an upstream arcing electrode 70, which is electrically connected to the stationary contact 14. As opening motion of them ovable contact 16 continues, the gas blast forces the downstream terminal of the are to transfer from them ovable contact 16 to orifice structure 39. which is electrically connected to the movable contact 16. The gas blast then impels the downstream terminal of the arc through the orifice opening 37 and nozzle 38 on to the upper end of the protective metallic tube 43. From there, the gas blast drives the downstream arc terminal downwardly and into the previously-described stagnation region adjacent the upstream surface 48 of the electrode 45. The arc then occupies the position generally shown at 46 with its upstream terminal on the upstream electrode and its downstream terminal on the n downstream electrode 45. When the arc is in this posiscavenge the arcing region of arcing products, thus preventing reignition thereof at an early current zero.

After interruption is completed, the blast valve 40 is returned in a downward direction to its solid line position of FIG. 1, thereby terminating the arc-extinguishing blast. This blast Valve-closing is effected by supplying pressurized air to the space between the two pistons 52 and 61. This pressurized air holds the movable contact 16 in its open position when the blast valve has closed.

It will be noted that the stationary contact 14 and its -associated upstream electrode 70 are supported on a hollow conductive stud 60. This stud 60 also serves to carry :current to and from the stationary contact 14 and the upstream electrode 70. The hollow stud 60 extends through the wall of the casing 12 and is supported on the casing 12 by tubular porcelain sleeves 62 and 64 surrounding the stud. These porcelain sleeves 62 and 64 together with the stud 60 constitute a terminal bushing of a generally conventional design.

For increasing the amount of current that the circuit breaker can interrupt, a number of important new features have been incorporated into the upsteam electrode 70. The manner in which these features contribute to increased interrupting capacity will soon be described, but first a description will be presented of the structure of these features.

For supporting the upstream electrode 70 on the stud 60, we provide a tubular adapter 65 that is suitably attached to the stud 60. Bolted to the adapter 65 is a tubular valve casing 66, to Iwhich is secured a tubular guide member 67 (FIG. 2). These tubular parts 66 and 67 are joined together by a suitable threaded joint 68. Attached to the upstream electrode 70 is a centrally located tubular valve stern 72 that is slid-ably supported within the guide member 67. Suitable slide bearings 73 of insulating material are provided between the stationary guide member 67 and the valve stern 72 to permit longitudinal movement of the stem within the guide member 67 under certain conditions soon to `be described.

The upstream electrode 70 is a cup-shaped Imember that comprises a semi-toroidal forward portion 74 and a tubular wall portion 76 joined to the semi-toroidal forward portion `at its outer periphery. At the rear end of the tubular wall portion 76, an annular radially-inwardly projecting flange 78 is provided. This flange 78 is detachably connected to the tubular wall portion, as by screws For carrying current between the tubular supporting structure 66, 67 and the upstream electrode 70, we provide a helically wound spring 80 encircling the tubular guide member 67. This spring 80 is electrically and mechanically connected at its forward end to a flange S2 projecting radially outward from the guide member 67 and integral therewith. The spring 80 is electrically and mechanically connected at its rear end to the inwardly projecting flange 78 on the electrode 70. This helically wound spring 80V is preferably made of a copper-beryllium alloy, and all of its turns except those at its extreme ends are coated with a thin layer of electrical insulation that prevents current through the spring from bypassing the turns. An insulating sleeve 83 encircling the guide member also aids in preventing any current from bypassing the turns of spring 80. Thus, current llowing between the tubular guide member 67 and the upstream electrode follows the helical path defined by the turns of spring 80.

Current ilowing through the helical path defined by the turns of spring 80 develops a radi-al magnetic field, as indicated by the lines of magnetic force 88 (FIG. 2). This radial magnetic field is used for rotating the upstream terminal of the arc in a manner that will soon be described.

For providing a mechanically strong connection between the spring 80 and the llange 82, the flange 82 is provided with a helical groove 84 into which the helical spring is threaded. This connection is best shown in FIG. 6. Four tapped holes are provided in the flange 82 at angularly-spaced points, and these holes register with holes 85a in the spring 80. Screws 86 extend through the holes in the spring and are threaded into the tapped holes 85 in the flange. These screws 86 clamp the walls of the groove in high pressure engagement with the adjacent surfaces of the spring 89 and also prevent the spring from unscre'wing from the groove 84. A similar connection is provided between the rear end of the spring 80 and the flange 78 on the electrode 70.

When the upstream are terminal is transferred from the stationary contact 14 to the electrode 70, as was described hereinabove, it is forced by the main air blast B enveloping the electrode '70 to move toward the forward face of the electrode. No current flows through the spring 80 until the arc is transferred to the electrode 70, but after this transfer has occurred, current flows through the spring 80 and produces the magnetic eld 88 referred to hereinabove. When the upstream arc terminal moves into the region adjacent the forward face of the electrode, the magnetic ileld 88 extends radially with respect to the axially-extending arc and is thus able to produce rotation of the upstream arc terminal about the central portion of the electrode.

For accentuating the forces urging the upstream are terminal toward the forward face of the electrode 70, slots 107 are provided in the upstream electrode. These slots extend radially outward from the central region of the electrode and then axially of the electrode in the tubular wall portion 76. These slots 107 force most 0i the current flowing through the electrode to an arc terminal thereon to follow a path that approaches the arc solely from the back of the electrode. Current is blocked from following circumferentially-extending paths approaching the arc. By forcing most of the current to follo'w a path that approaches the arc from the back of the electrode, a more delinite loop bowing toward the front face of the electrode is defined. This results in a greater magnetic force urging the arc toward the forward face of the electrode, thus accelerating movement of the upstream terminal to the forward face of the electrode.

Another function served by the coiled spring 80 is to provide a force on the upstream electrode 70 urging it to the right into its position of FIG. 2. In this position, a movable valve member 90 attached to the valve stem 72 abuts against a stationary annular valve seat 92, thus blocking further movement of the upstream electrode 70 to the right.

There is an auxiliary blast passage leading through the upstream electrode 70 is the hollow stud 60 to atmosphere. The portion of this auxiliary blast passage that extends through the electrode 70 is designated 95 and the portion extending through the stud 60 is designated 96. The auxiliary blast passage is normally closed by means of the normally-closed auxiliary blast valve 9i), 92. But under high current conditions, as will soon be described, the movable auxiliary blast valve member 90 is moved to the left to open the auxiliary blast valve 90, 92, as shown in FIG. 3. This permits high pressure air to flow through the auxiliary blast passage 95, 96 via the thenopen auxiliary blast valve 90, 92. The path of the auxiliary blast is indicated by the arrows 97 in FIG. 3, where the auxiliary blast can be seen passing through openings 99 and the stem 72 and then through the central opening annular valve seat 92.

The force for producing the above-described opening of the auxiliary blast valve 90, 92 is derived from current through the coiled spring 80. In a well-known manner, current flowing through the spring 80 will develop magnetic force that tends to draw together the turns of the spring. This action is opposed by the high pressure air in casing 12 acting to the right on the movable valve member 90 and, to a lesser extent, by the resilience of the spring 80. But when the current exceeds a predetermined value, suli'icient magnetic force is developed to overcome this opposition and move the turns of the turns of the spring toward each. This forces the flange 78 and the upstream electrode 70 to the left from their position on FIG. 2 to that of FIG. 3. This leftward motion is transmitted through the valve stem 72 to effect opening of the movable' valve member 90.

The distance that the upstream electrode moves to the left can be controlled by a suitable stop. In the illustrated embodiment, we rely upon the spring 80 itself to provide this stop. When the turns of the spring engage each other, as shown in FIG. 3, leftward motion of the upstream electrode 70 is terminated.

The spring Si) can be designed so that the electromagnetic forces effect the above-described leftward motion of the electrode at any desired current level, assuming a given pressure in the tank 12. In a preferred embodiment of the invention, we design the spring 80 so that the electromagnetic forces produce this leftward motion of the electrode when the current through the spring 80 is between 15,000 and 20,000 amperes, peak, assuming normal pressure of S p.s.i. is present in the tank.

When the current drops below this value, as when the arc is extinguished, the above-described opposing forces overcome the magnetic force :between the turns of the spring 80 and thus return the movable valve member 90 to its closed position of FIG. 2.

If the circuit breaker is called upon to interrupt a current of a moderate or relatively low value, i.e., below 15,000 amperes peak, the current through the coiled spring 80 is insuflicient to move the upstream electrodes out of its normal position of FIG. l. It is thus insufficient to open the auxiliary blast valve 90, 92. During such interruptions, the movable blast valve 40 opens and produces the main blast of air B that moves the arc into the position of FIG. l, but there is no auxiliary blast through the auxiliary blast passage 95, 96. There is, however, a radial magnetic field such as s'hown at 88 that acts to magnetically drive the upstream terminal of the arc 46 in a circular path about the central region of the electrode 70. This radial-magnetic field 88 is produced by current flowing through coil 80, as was previously described.

If lthe circuit breaker is called upon to interrupt a high current, the main blast B again moves the arc into the position illustrated in FIG. l. This results in the high current flowing through the coil 80 developing a suiiicient magnetic attraction between the turns of the coil spring 80 to drive the electrode 70 leftward into its position of FIG. 3. This leftward motion reduces the distance between the upstream electrode 70 and the orifice 39 and also opens the auxiliary blast valve 90, 92.

The shorter -spacing between the upstream electrode 70 and the orifice member 39 improves the interrupting ability of the circuit breaker, enabling it to interrupt appreciably higher currents than it could with the relatively long original gap length. We attribute the .increased interrupting capacity, in part, to the higher velocity of the air in the region between the electrode 70 and the orifice member 39 when the spacing between these parts is reduced. Some of the increased interrupting capacity also -appears to be attributable to the fact that the shorter gap between the electrode 70 and the orifice member 39 causes less arc energy to be released upstream of the orifice.

As soon as the arc is extinguished, no further current iiows through the coiled spring S0 and the magnetic attraction between the turns of the spring will drop sharply. This allows the upstream electrode 70l to be quickly returned to its normal position of FIG. 2 by the air pressure in the tank 12 acting on the electrode 70 and the movable valve member 90. This rapid reestablishment of the initial relatively great gap length serves the highly desirable purpose of increasing the dielectric strength across the gap immediately after circuit interruption is completed, thus reducing the chances that this gap will be sparked over tby any high voltage transients occurring during or after this crucial period.

When the upstream electrode 70 moved to the left, as above described, it also opened the auxiliary blast valve 90, 92 since the movable valve member 90 is mechanically connected to the electrode 70 through the valve stem 72. `Opening of the auxiliary blast valve caused an auxiliary blast to flow through the blast passage 9S in the upstream electrode, as was explained hereinabove. This auxiliary blast has been found to further increase the interrupting capacity of the circuit breaker. This increase in interrupting capacity appears to be attributable to irnproved scavenging that occurs in the region of the upstream electrode. This scavenging action quickly removes arcing products from in front of the upstream electrode, replacing them with fresh gas of much greater dielectric strength.

In some cases, the auxiliary blast will drive the upstream terminal of the arc inside the auxiliary blast passage 95. For receiving the arc terminal when it is driven into this position, an arcing probe of a refractory material is provided. The arc terminal will attach to this probe 100, and this will prevent damage to adjacent parts of the auxiliary blast valve.

In those cases in which the upstream arc terminal does enter the auxiliary blast passage 95 and attach to the probe 109, the arc column will -be generally parallel to the radial field 88. Under these conditions, there will be no substantial arc-rotating fonce. But prior to entry of the arc into the passage 95 there will be an arc-rotating force that rotates the arc to reduce the quantity of arcing products generated. Also, under lower current interrupting conditions when no auxiliary blast is present, the upstream arc terminal does not enter the auxiliary blast passage 95, and the radial magnetic field 88 is effective to produce arc rotation. This desirably serves to reduce arc erosion of the upstream electrode. This arc rotation also allows higher currents to be interrupted with the relatively long gap that is present between the upstream electrode 70 and and orifice member 39.

The fact that the auxiliary blast valve 90, 92 is maintained closed for low and moderate currents is advantageous since it greatly reduces the number of times that the valve will be called upon to open and close. This is particularly so since a high current fault is ordinarily a very rare occurrence. This reduced frequency of operation reduces wear on the valve elements, thereby materially prolonging their life and improving the reliability of the auxiliary blast valve.

Although the above-described form of our invention includes an auxiliary blast valve, our invention in its broader aspects icomprehends an arangement in which there is no auxiliary lblast Valve or auxiliary blast passage. In such an arrangement, the only blast is the main blast at B. The arc-rotating means and gap length control means are still present, however, lto aid circuit interruption.

Our invention in its broader aspects also comprehends other current responsive means instead of coiled spring 80 for changing the electrode spacing during high current interruptions.

In the modified form of my invention shown in FIG. 7, the upstream arc terminal is normally prevented from entering the auxiliary blast passage 95. In this connection, a tubular insert of a suitable insulating material is included in the upstream electrode 70. This insert 120 provides a thick coating of insulating material on the portion of the upstream electrode surrounding the mouth of auxiliary blast passage 95, thus blocking the( arc terminal from moving into the auxiliary blast passage. By maintaining the upstream arc terminal on the forward portion 74 of the upstream electrode, the arc is kept in a position where the magnetic field from coil 80 extends transversely of the arc and is able to produce effective arc-rotation about the longitudinal axis of passage 95. A preferred material for the insert 120 is polytetrafiuoroethylene, sold under the trademark Tefion.

While we have shown and described particular embodiments of our invention, it will be obvious to those skilled in the art that various changes and modifications may be made without departing from our invention in its `broader aspects, and we, therefore, intend in the appended claims to cover all such changes and modifications as fall within the true spirit and scope of our invention.

What we claim as new and desired to secure by Letters Patent of the lUnited States is:

1. An electric circuit breaker of the prising:

(a) a pair of spaced-apart electrodes between which an arc is established during circuit interruption,

(Ib) one of said electrodes being relatively movable with respect to the other of said electrodes,

(c) said one electrode having a normal position where it is spaced by a predetermined first amount from said other electrode,

(d) means responsive to arcing current flowing through said one electrode for moving said one electrode toward said other electrode when the arcing current through said one electrode exceeds a predetermined value,

(e) means for holding said one electrode in a position spaced from said other electrode by a predetermined second amount substantially smaller than said first amount during the passage of high currents through said one electrode and arc,

(f) means for directing a blast of gas through the space between said electrodes while said arc is present therebetween, whereby to aid in extinguishing said arc,

(g) and means responsive to a fall in said arcing current to a predetermined level for returning said one electrode to its normal position spaced by said predetermined first amount from said other electrode.

2. The circuit breaker of claim 1 in combination with arc-rotating means for developing a magnetic field extending transversely of said arc for rotating at least a portion of said arc during the circuit-interrupting operation.

3. The circuit breaker of claim 1 in which the means for moving said one electrode toward the other electrode comprises an electromagnet that is energized by arcing current and develops in response to energization a magnetic field extending transversely of said arc and capable of rotating said arc.

4. The circuit breaker of claim 1 in which:

(a) said one electrode is of a hollow construction and said means responsive to arcing current comprises a coil located within said hollow electrode,

(b) a conductive member is provided projecting into said hollow electrode from the back thereof for supporting said electrode and for carrying current to and from said electrode, and

(c) said coil encircles said conductive member and is connected at one end to said conductive member and at its opposite end to a portion of said one electrode.

5. The circuit breaker of claim 1 in which said means for moving said one electrode toward said other electrode comprises:

(a) a coil connected in series with said one electrode, said coil having turns that are normally spaced from each other and which move toward each other when tra-versed by high currents,

(b) and means for moving said one electrode toward said other electrode in response to motion of said turns toward each other.

6. The circuit breaker of claim 1 in combination with:

(a) a main blast passage adjacent said other electrode through which the gas blast of claim 1 is directed,

(b) an auxiliary blast passage extending through said one electrode,

gas-blast type com- (c) a normally-closed auxiliary blast valve for controlling fiows through said auxiliary blast passage, (d) means controlled by movement of said one electrode toward said other electrode for opening said auxiliary blast valve to produce an auxiliary blast through said auxiliary blast passage during high current interruptions,

(e) and means for closing said auxiliary blast valve in response to said return movement of said one electrode to its normal position.

7. An electric circuit breaker of the gas-blast type comprising:

(a) a pair of spaced-apart electrodes between which an arc is established during circuit interruption,

(b) an orifice having an opening through which said arc is adapted to extend when present between said electrodes,

(c) means for causing a stream of gas to pass through said orifice opening axially of said are about the periphery of the arc,

(d) means for mounting the electrode upstream from said orifice for movement toward and away from said orifice,

(e) said upstream electrode having a normal position spaced by a relatively large amount from said orifice,

(f) actuating means responsive to arcing current above a predetermined value through said upstream electrode for moving said upstream electrode from its normal position toward said orifice, whereby to increase the gas velocity in the region between said orifice and said upstream electrode,

(g) means for limiting movement of said upstream electrode toward said orifice after the spacing between said upstream electrode and said orifice has been reduced to a predetermined finite value by said actuating means,

(h) and means responsive to a reduction in said arcing current to a predetermined level for returning said upstream electrode to its normal position, thereby reestablishing said relatively large amount of spacing between said orifice and said upstream electrode.

8. The circuit breaker of claim 7 in combination with:

(a) an auxiliary blast passage extending through said upstream electrode,

(b) a normally-closed auxiliary blast valve for controlling fiow through said auxiliary blast passage, (c) and means controlled by movement of said upstream electrode toward said orifice for opening said auxiliary blast valve to produce an auxiliary blast through said auxiliary passage during high current interruptions.

v9. An electric circuit breaker of the comprising:

(a) a pair of spaced-apart electrodes between which an arc is established during circuit interruption, (b) an orifice having an opening through which said arc is adapted to extend when present between said electrodes,

(c) means for causing a main blast of gas to pass through said orifice opening axially of said arc about the arc periphery during both high current and low current interruptions,

(c') said main blast fiowing first past one of said electrodes, then through said orifice, and then past the other of said electrodes,

(d) an auxiliary blast passage extending through said one electrode from the region between said electrodes to a region of lower pressure,

(e) a normally-closed auxiliary blast valve in said auxiliary blast passage for controlling flow through said auxiliary blast passage and blocking fiow therethrough when closed,

(f) means responsive to current through said breaker above a predetermined value for opening said normally-closed auxiliary blast valve during high curgas-blast type 1 1 rent interruptions to produce an auxiliary blast during high current interruptions that flows through said auxiliary blast passage from the region between said electrodes, (g) and means for maintaining said auxiliary blast valve closed during low current interruptions. 10. The circuit lbreaker of claim 9 in which said current-responsive means of limitation (t) is responsive to current through said arc.

ROBERT S.

Aspey et al.

Alderman.

Amalric 200-148 Lerch 200-148 Leeds 200--148 Barkan 200-148 Cromer et al. 200-145 XR FOREIGN PATENTS Great Britain. Great Britain.

MACON, Primary Examiner.

Us. C1. X.R. 

